Imagine that during the 40s, a witness from Europe comes and tells you of the horrors of the Holocaust. These things, so unthinkable that they hardly seem possible, so evil that Peter Kreeft argues they’re possible only with satanic help, would sound absurd: like war-time propaganda. The Witness will do everything she can to establish the veracity of her claims. Of course, it’s also possible for a person to hear the Witness and believe the message for wholly unreasonable causes, but a smart listener will gauge how reliable she seems. And note: listeners who say “these claims are outrageous, so they must be false” are less reasonable those who say “these claims are outrageous, but well supported by available evidence, so they must be true.” Which is why atheists who mock Christians for believing in an “Old Man in the Sky” are just showing a dogmatic abandonment of reason.
Christianity presents an equally shocking claim, for opposite reasons. And like the Holocaust (which has an overwhelming weight of the evidence, but some recalcitrant doubters), Christianity can prove a great deal of Her story through reason. She can point to the sky and say, “Look! It’s beautiful. Evolution (particularly inorganic evolution) doesn’t lead to transcendence or beauty.” Or She can say, “Look! Truth exists!” Because at heart, Reason is built upon its Faith in Truth. Which is why Pope Benedict accurately call Catholicism “a reasonable Faith.”